869
FXUS61 KCAR 181831
AFDCAR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CARIBOU ME
231 PM EDT MON MAY 18 2026
WHAT HAS CHANGED
ADDED SMALL HAIL AND GUSTY WINDS IN STORMS FOR TUESDAY
LOWERED LOWS FOR FRIDAY NIGHT.
KEY MESSAGES
1) WARM TO VERY WARM WITH A CHANCE FOR THUNDERSTORMS TUESDAY
AND WEDNESDAY AFTERNOON. A FEW STRONGER STORMS ARE POSSIBLE.
2) BELOW AVERAGE TEMPERATURES ARE EXPECTED THURSDAY AND
THURSDAY NIGHT. NEAR FREEZING TEMPERATURES ARE POSSIBLE EARLY
FRIDAY MORNING ACROSS THE NORTH, WHICH MAY REQUIRE ACTIONS TO
PROTECT VULNERABLE PLANTS.
DISCUSSION
KEY MESSAGE 1...
WARM TO VERY WARM WITH A CHANCE FOR THUNDERSTORMS TUESDAY
AND WEDNESDAY AFTERNOON. A FEW STRONGER STORMS ARE POSSIBLE.
KEY MESSAGE 1 DESCRIPTION...
A LITTLE SHORTWAVE AHEAD OF A LARGER TROUGH WILL DRAPE A WARM
FRONT OVER THE AREA THAT MOVES NORTH THROUGH THE DAY TUESDAY.
THIS WARM FRONT WILL BRING WARM TEMPERATURES AND INSTABILITY.
SOME CLOUD COVER COULD PREVENT INCREASED DAYTIME HEATING WHICH
COULD LIMIT CONVECTION. THUNDERSTORM CHANCES ARE HIGHEST IN
CENTRAL AND SOUTH MAINE. STORMS MAY CONTAIN GUSTY WINDS AND
POTENTIALLY SMALL HAIL AND LIGHTNING. THE RISK OF A TORNADO
CANNOT BE RULED OUT.
THE MODELS HAVE SIGNIFICANTLY SLOWED DOWN THE PROGRESSION OF THE
COLD FRONT THROUGH THE REGION, WITH IT NOW PROGGED TO MOVE
THROUGH MAINLY ON WEDNESDAY NIGHT. THIS IS DUE TO THE FRONT
BEING ALMOST PARALLEL TO THE WINDS ALOFT AS WELL AS SUBSIDENCE
UNDER THE RIDGING EXITING TO THE EAST ON WEDNESDAY. AS A
RESULT, WEDNESDAY LIKELY WILL BE THE WARMEST DAY OF THE WEEK
ACROSS MOST OF EASTERN AND SOUTH CENTRAL MAINE. BECAUSE OF THIS,
MODELS ARE NOW KEYING ON CONVECTION FIRING MAINLY ALONG/JUST
NORTH OF THE SEA BREEZE FRONT OVER DOWNEAST MAINE AND INTO THE
BANGOR REGION. WITH AROUND 1000 J/KG OF CAPE, 40-50KT OF BULK
SHEAR, COULD SEE STRONG TO LOCALLY SEVERE STORMS ACROSS THIS
REGION, WITH THE MAIN THREAT BEING STRONG GUSTY WINDS AND HAIL.
THE TORNADO THREAT REMAINS NON- ZERO, WITH ENERGY HELICITY INDEX
OF 0.5 TO 1, 0-3KM SRH 100-175 M2/S2 AND 0-1KM SRH 50-100
M2/S2. HOWEVER THE THREAT IS MUCH LOWER THAN ON TUESDAY.
ALSO OF NOTE ON WEDNESDAY IS THAT THE WINDS SHOULD BE RATHER
GUSTY WITH GUSTS OF 30-35 MPH, WITH SOME PEAK GUSTS TO AROUND 40
MPH ACROSS THE SAINT JOHN VALLEY.
HIGHS ON WEDNESDAY SHOULD RUN 15-20 DEGREES ABOVE NORMAL. WITH
DEWPOINTS PEAKING OUT AROUND 60, AND FALLING OFF IN THE
AFTERNOON, THIS SHOULD LIMIT APPARENT TEMPERATURES TO THE UPPER
70S TO LOWER 80S ACROSS MOST OF EASTERN AND CENTRAL MAINE, WITH
LOW-MID 70S ACROSS THE NORTH WOODS.
KEY MESSAGE 2...
BELOW AVERAGE TEMPERATURES ARE EXPECTED THURSDAY AND
THURSDAY NIGHT. NEAR FREEZING TEMPERATURES ARE POSSIBLE EARLY
FRIDAY MORNING ACROSS THE NORTH, WHICH MAY REQUIRE ACTIONS TO
PROTECT VULNERABLE PLANTS.
KEY MESSAGE 2 DESCRIPTION...
NW FLOW IN THE LOW LEVELS ADVECTS IN A MUCH COOLER AIR MASS INTO
THE REGION THURSDAY INTO THURSDAY NIGHT, AS CANADIAN HIGH
PRESSURE BUILDS IN FROM THE NORTHWEST AND WEST. THIS HIGH THEN
BUILDS OVER THE AREA THROUGH FRIDAY NIGHT. THE RESULT WILL BE
LOWS RUNNING 5-10 DEGREES BELOW NORMAL BOTH NIGHTS. THIS SHOULD
RESULT IN FROST MAINLY ACROSS NORTHERN MAINE. ZONES 2, 5, 6,
10, 11, 31 AND 32 GET ADDED TO THE FROST FREEZE PROGRAM ON MAY
21, SO A FROST ADVISORY COULD BE NEEDED FOR AT LEAST PART OF
THAT AREA ON BOTH NIGHTS IF CURRENT FORECAST TRENDS HOLD.
AVIATION /18Z MONDAY THROUGH SATURDAY/
TONIGHT...VFR FOR ALL TERMINALS EXCEPT FOR KBHB, WHICH COULD
REACH IFR IN SOME MARINE FOG. LLWS POSSIBLE AT NORTHERN
TERMINALS. SOME RAIN SHOWERS AT FAR NORTHERN TERMINALS. SW WINDS
AT 5-10 KT AND GUSTS TO 15 KT.
TUESDAY...MVFR, POTENTIALLY LOWER IN TERMINALS WITH SEVERE
THUNDERSTORMS. BEST CHANCE FOR THUNDERSTORMS IS DURING THE
AFTERNOON INTO EVENING. HEAVY RAIN, LIGHTNING, SMALL HAIL, AND
GUSTY WINDS ARE POSSIBLE IN THESE THUNDERSTORMS. S WIND AT 5 KT
SHIFTING TO W WINDS AT 5-10 KT. GUSTS TO 20 KT.
TUESDAY NIGHT...MVFR POSSIBLE AT NORTHERN TERMINALS, IFR
POSSIBLE AT KFVE. VFR ELSEWHERE. SOME RAIN SHOWERS AT NORTHERN
TERMINALS POSSIBLE. WSW WINDS 5 TO 10 KT, RAMPING UP THROUGH THE
NIGHT, WITH GUSTS TO 20 KT.
WEDNESDAY: LOW CHANCE OF MVFR EARLY AT NORTHERN TERMINALS,
OTHERWISE VFR. TEMPO MVFR/IFR IS POSSIBLE AT SOUTHERN TERMINALS
IN ANY STRONG CONVECTION. W-WNW WINDS G25-30KT LIKELY WITH A
CHANCE OF GUSTS TO 35KT AT FAR NORTHERN TERMINALS.
WEDNESDAY NIGHT-SATURDAY: VFR. NW WINDS G20-30KT POSSIBLE DURING
THE DAY THURSDAY AND FRIDAY.
MARINE
WINDS STAY BELOW SCA CRITERIA MONDAY NIGHT, WITH SOME GUSTS OF
25 KT ON OUTER WATERS TUESDAY OUT OF THE SOUTHWEST. SOME FOG IS
POSSIBLE MONDAY NIGHT. RAIN SHOWERS AND SOME THUNDERSTORMS ARE
POSSIBLE ON TUESDAY.
MARGINAL SMALL CRAFT ADVISORY SEAS AROUND 4 TO 6 FEET ARE
POSSIBLE OVER THE COASTAL OCEAN WATERS TUESDAY NIGHT. WAVE
HEIGHTS TO AROUND 5 TO 7 FEET ALONG WITH GUSTS UP TO 25 KT ARE
POSSIBLE ACROSS THE OUTER WATERS.
SMALL CRAFT CONDITIONS ARE LIKELY ACROSS THE COASTAL WATERS
WEDNESDAY THROUGH THURSDAY, WITH GUSTS OF 25-30KT AND SEAS OF
4-6 FT OVER THE OUTER WATERS DURING THIS TIME FRAME AS WELL.
FROM THURSDAY NIGHT THROUGH SATURDAY, SUB-SCA CONDITIONS ARE
PREDICTED FOR THE COASTAL WATERS AND WINDS LESS THAN 25 KT AND
SEAS OF 5 FT OR LESS ARE FORECAST FOR THE OUTER WATERS.
THERE IS A SMALL CHANCE FOR SOME STRONG THUNDERSTORMS OVER THE
COASTAL WATERS WEDNESDAY AFTERNOON AND EARLY WEDNESDAY EVENING.
SEA SURFACE TEMPERATURES REMAIN VERY COLD, BUT ARE BEGINNING TO
MODERATE INTO THE MID 40S.
CAR WATCHES/WARNINGS/ADVISORIES
ME...NONE.
MARINE...NONE.
DISCUSSION...TF/PM/JS
AVIATION...TF/PM/JS
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